This invention relates generally to wireless communication systems, and more particularly, to systems and methods providing local wireless communications between radio units within a talk group.
Wireless communication systems may provide communication between individual users and/or between groups of users, such as group calls in Push-to-Talk (PTT) cellular wireless communication systems. Group based communications also may be provided in other types of communication systems, such as public safety or professional communication systems, as well as others. Radio frequency communication between cellular or radio units allows messages to be communicated between two users or between a group of users. In particular, using these communication systems with PTT services, which may include a dispatch mode of operation, wherein a dispatcher from a central location communicates with one or more radio units, or where multiple radios or cellular units inter-communicate, work groups performing a job or project or emergency personnel responding to an emergency at a building may communicate.
Group communications require connection of multiple radios or cellular units. Systems are known that provide multicast communications where multiple users share a single call stream or channel. In other known systems, group calls are realized using individual call streams sent to each user. Multicast communications are typically preferred over single stream communications because multicast communications require less bandwidth for group calls. However, group calls may be desirable or needed on systems that do not support multicast communications. Accordingly, single stream communications must be provided. For example, Enhanced Data rates for GSM Evolution (EDGE) communication systems do not support multicast communications, but may be used in applications where group communications are desirable or needed. In the EDGE systems, group calls are sent over single streams of the cellular data service offered by EDGE using Voice-over-Internet-Protocol (VoIP).
In communication systems wherein group calls require individual communication streams, if users are in different communication cells, bandwidth usage is not minimized with multicast communications because the data must be sent at least once to each cell containing a user. However, if multiple users on the same group call are in the same communication cell, multiple single communication streams transmitting the same data must be sent. Depending on the number of users on the group call in the single communication cell, the data can overload the capacity or bandwidth of the communication cell.